How hard would it be to explicitly exclude recipes? I imagine there would need to be some type of config that was read in, and if a recipe matched it wouldn't be displayed as an option.

Quite hard to get right. The result alone isn't enough as, for example, ingots can be crafted from nuggets or blocks, and the ingredients are hard, since there's so many recipes that take, for example "any kind of wood".

So certainly not something I'll implement, especially as I fail to see a good use case for that.